Did KoKo talk when she communicated her tooth ache by sign language? I would say yes. http://en.wikipedia.org/wiki/Koko_(gorilla) Do meerkats engage in service exchange? http://nationalzoo.si.edu/Publications/ZooGoer/2007/1/meerkats.cfm Trickier, but I would again say yes. It has always fascinated me that so many economists wish desperately to see humans as non-animals. This may well explain some failures to understand human behavior. http://www.bushorchimp.com/pics.html Alan Isaac PS None of this is meant to deny that the human ability to handle abstraction (a *quantitative* difference, which varies substantially among humans) has had qualitative implications.